In the context of this patent description and the following claims, the gearshift can be either a rear one, which shifts a chain between different sprockets associated with a rear wheel of the bicycle, or a front one, which shifts the chain between different crowns associated with pedal cranks.
Recently bicycle gearshifts with motorized actuation have become widespread, wherein the displacement of the derailleur that deviates the chain takes place under the action of a drive member that is electronically operated. In developing such gearshifts, a great deal of attention has been given to the quality of actuation, meaning the ability of the gearshift to perform gear-shifting quickly and precisely at least to the same degree as a conventional manually actuated gearshift. Inventors have, however, realized that in normal use the performance of a motorized actuating gearshift is often compromised by even small damage. This is often the consequence of unseen knocks received by the gearshift itself.
Indeed, with gearshifts of this type, the actuation mechanism is a system that is mechanically coupled to the drive member. In the case of knocks, due for example to the bicycle falling or even due only to loading, unloading and transportation on a vehicle, the gearshift can undergo various amounts of damage. A particularly serious knock can, in the most serious of cases, cause the breaking of some members of the gearshift. Less serious knocks can, on the other hand, cause small deformations or even just small mutual displacements of the members of the gearshift, often not immediately noticeable at a glance, but still such as to compromise the precision and therefore the proper operation of the gearshift. Such deformations or displacements can, in other cases, be determined during gear-shifting by temporary locking of the mechanism with respect to the drive member, as sometimes occurs following mechanical interference between the chain and sprockets.
The problem to be solved by the present invention is that of protecting the actuation mechanism of a motorized actuation gearshift in a simple and efficient manner.